There have been proposed home-use entertainment systems capable of not only executing video game programs but also reproducing videos. This type of home-use entertainment system has a three-dimensional image generated by a graphics processing unit (GPU) using polygons (e.g., see PTL 1). For this type of system, it is always a challenge to obtain a trade-off between responsiveness for image display and image quality. Various measures have thus been devised to render high-resolution images at high speed.
For example, what is widely known is the multum in parvo (MIP) mapping technique that involves preparing a texture image representing a background at multiple resolutions so that the image may be switched from one resolution to another when rendered (e.g., see PTL 2). MIP map data is prepared beforehand by taking time to obtain high resolutions. At the time of image display, the map data need only be referenced or interpolated to efficiently generate a high-quality display image. Also proposed are techniques for linearly approximating coordinate transformation from the texture image to the display image and identifying texels in the texture image corresponding to positions in the display image by inversion of the transformation (e.g., see NPL 1).